Hemodynamic monitoring is useful in the care of patients, for example in the intensive care unit (ICU) or during surgery. The ICU provides a place for monitoring and care of patients with potentially severe physiological instability requiring advanced artificial life support. Within this context, hemodynamic monitoring is used to identify hemodynamic instability and its cause and monitor the response to therapy. Medical technological advances have enabled monitoring, display, and assessment of many physiological variables (Pinsky M R and Payen D, Crit. Care 2005, 566-572), yet the utility of some aspects of hemodynamic monitoring is unproven. It is the commonly available technologies where clinical studies have demonstrated relevance in terms of improved patient outcome. Physiological measures available from commonly available monitoring devices are given in Table 1.
Table 1. Hemodynamic Monitoring Defined Primary Hemodynamic Variables
A. Non-Invasive Monitoring
1. Electrocardiogram (ECG)
Heart rate, dysrhythmnias, heart rate variability
2. Pulse Oximetry
SPO2, heart rate
3. Arterial Pressure
                Sphygmomanometer                    Systolic and diastolic arterial pressure, heart rate, pulsus paradoxus4. Central Venous PressureJugular venous distention, hepato-jugular reflux, cannon waves (A-V dissociation).B. Invasive Monitoring1. Arterial CatheterizationSystolic, diastolic and mean arterial pressure, heart rate, pulse pressureArterial pressure waveform analysisStroke volume and cardiac output, pulse pressure variation, systolic pressure variation and stroke volume variation2. Central venous catheterizationCentral venous pressure, venous pressure waveform (“v” waves), respiratory variations                        Thermodilution indices (when coupled to an arterial thermal sensor)Stroke volume and cardiac output, intrathoracic blood volume, global end-diastolic volume and oxygen delivery (DO2)3. Pulmonary Artery CatheterSystolic, diastolic and mean pulmonary arterial pressure, pressure waveform (“v” waves), pulmonary artery occlusion pressureMixed venous blood gas analysis—SvO2Thermodilution cardiac output (by thermodilution either intermittent or continuous)Stroke volume and cardiac output, RV ejection fraction and RV end-diastolic volume4. Esophageal Doppler Monitoring        Stroke volume, cardiac output and stroke volume variation, flow corrected time interval        
Despite the many options available, most ICUs predominantly monitor and display only blood pressure, heart rate (HR) and pulse oximetry (SpO2). LIDCOplus is a hemodynamic monitor produced by LIDCO Group Plc. The version 4 software for this monitor allows a user to select some specific hemodynamic parameters for display on a shortened time basis. This short term user scalable display is superimposed over the background general trend data and while useful thus obscures sections of the trend data. Improved displays are required which are more appropriate to the requirements of maintaining the hemodynamics of a patient.